#include<iostream>
#include<cstdio>
#include<algorithm>
using namespace std;
const int N = 510, INF = 1e9;
int n;
int a[N][N];
int f[N][N];
int main()
{
	scanf("%d", &n);
	for (int i = 1 ; i <= n ; ++i)
		for (int j = 1 ; j <= i ; ++j)
			scanf("%d", a[i] + j);
	for (int i = 0 ; i <= n ; ++i)
		for (int j = 0 ; j <= i ; ++j)
			f[i][j] = -INF;
	f[1][1] = a[1][1];
	for (int i = 2 ; i <= n ; ++i)
		for (int j = 1 ; j <= i ; ++j)
			f[i][j] = max(f[i - 1][j - 1], f[i - 1][j]) + a[i][j];
	int res = -INF;
	for (int i = 1 ; i <= n ; ++i)
		res = max(res, f[n][i]);
	printf("%d\n", res);
	return 0;
}
